If nuclear negotiations fail and conflict arises with the United States, Iran will strike American bases in the region, Defense Minister Aziz Nasirzadeh said Wednesday, days ahead of a planned sixth round of Iran-U.S. nuclear talks.

"Some officials on the other side threaten conflict if negotiations don't come to fruition. If a conflict is imposed on us... all U.S. bases are within our reach and we will boldly target them in host countries," Nasirzadeh said during a press conference.

President Donald Trump has not ruled out bombing Iran if it does not reach a new nuclear deal.

The next round of talks is due this week, with Trump saying negotiations would be held on Thursday while Tehran says they will take place on Sunday in Oman.

Iran is expected to hand a counter-proposal to a previous U.S. offer for a nuclear deal it rejected, with Trump reacting Tuesday that Iran is becoming "much more aggressive" in nuclear talks.

Nasirzadeh added Tehran recently tested a missile with a two-ton warhead and does not accept limitations. Supreme Leader Ayatollah Ali Khamenei had said in February that Iran should further develop its military, including its missiles.